rigourousness vs harshness

rigourousness and harshness both are nouns.

Word	Noun	Adjective	Verb	Adverb
rigourousness	Yes	No	No	No
harshness	Yes	No	No	No

As nouns, rigourousness and harshness are synonyms defined as:

Other synonyms of rigourousness include hardness, inclemency, rigor, rigorousness, rigour, severeness, severity, stiffness.

rigourousness (noun)	harshness (noun)
something hard to endure	the quality of being harsh or rough or grating to the senses
excessive sternness	excessive sternness
	the roughness of a substance that causes abrasions
	the quality of being cruel and causing tension or annoyance